This invention relates generally to radiotelephones and, in particular, to radiotelephones or mobile stations such as those capable of operation with a cellular network and/or a personal communications network.
In one presently specified air interface standard (IS-136) a Short Message Service Broadcast Channel (S-BCCH) is specified for use in sending point-to-multipoint messages to mobile stations, such as radiotelephones. A maximum number of 15 slots per Superframe may be assigned to the S-BCCH logical channel. The S-BCCH is considered as a continuous channel even if more than one slot is allocated to the S-BCCH.
The SMS frame may be defined as a sequence of 24 Superframes which are aligned with a Hyperframe (HF) counter. Thus, the number of slots assigned to the SMS frame are 0, 24, 48, 72, depending on how many slots per Superframe are assigned to BCCH.
The Hyperframe (HF) counter and a Primary Superframe (SF) indicator can be provided in the BCCH. These two counters together (2*HF Counter+Primary SF indicator) constitute a Superframe counter. A SMS frame is defined to be a single complete cycle (0-23) of the SF counter. The SMS frame is aligned to start at a HF counter value of 0, and also when the Primary Superframe indicator equals 0. The SF counter provides SMS frame synchronization information to the mobile station.
SMS subchannels are defined to allow different repetition cycles for different messages. Each subchannel has its own repetition cycle defined in terms of units of SMS frames. SMS frames are grouped into the SMS subchannels. Within each subchannel, a repetition cycle is defined (in units of SMS frames) with which the SMS broadcast message sequences contained in the SMS sub-channel are repeated. The SMS broadcast subchannel cycle may range from 1 to N SMS frames in length. Within each subchannel, the first S-BCCH slot within each SMS frame contains a header that describes the structure of the subchannel. Up to four subchannels may be defined. If more than one subchannel exists, the subchannels are time-multiplexed onto the S-BCCH channel on a SMS frame basis. If a SMS subchannel block is defined to consist of one SMS frame from each subchannel, placed in ascending order of subchannel number, then the multiplexed subchannels can be defined as the repetition of these subchannel blocks. The number of subchannels and the identity of the subchannel to which an SMS frame belongs are specified in the SMS frame header.
According to SMS header information found in the first slot in any SMS frame, the set of messages in SMS(i) may span M(i) number of SMS frames before a cycle is completed. M(i) is the length of the sub-channel cycle. The SMS frame number within the subchannel cycle is referred to as the phase of the subchannel cycle.
A number of different BCCH message categories can be defined by network operators. These include Emergency Information messages, Time and Date messages, Overload Class messages, System Identity messages, and Broadcast messages. Each BCCH message typically includes a number of fields of information. These fields can include: a Protocol Discriminator field, a Message Type field, a SMS Message ID field, and a Text Message Data field.
The Broadcast Message category field is coded to provide a number of different types of message category identifiers. These include, by example, emergency numbers and road-side information, toll gate information, airline departure/arrival information, weather-related information, news, and financial information.
There exist at least two previous proposals to enable a cell broadcast SMS operation (i.e., PN3011 (Apr. 8, 1994) and a June 1995 S-BCCH proposal). However, neither of these previous proposals provides a totally satisfactory method to manage and facilitate the access to, and use of, S-BCCH messages.
It is thus a first object of this invention to provide an improved method for providing a cell-based broadcast service.
It is another object of this invention to provide enhancements to existing or proposed S-BCCH protocols so as to facilitate the ease of use of the cell broadcast service.
It is one further object of this invention to define and provide index messages that contain information about cell broadcast messages so as to facilitate the ease of use of the cell broadcast service.
The foregoing and other problems are overcome and the objects of the invention are realized by methods and apparatus in accordance with embodiments of this invention. A method of this invention is disclosed for operating a cellular network and mobile station for transmitting and receiving, respectively, cell broadcast messages.
More particularly, this invention provides for the use of an index message in a Cell Broadcast Service. An index message is considered herein to be a special type of Cell Broadcast message which contains general information about actual broadcast messages. The index message is transmitted in a predetermined logical S-BCCH subchannel, and contains information elements such as (a) message overviews or summaries for each cell broadcast message, (b) information concerning emergency messages, (c) information concerning the language used in different broadcast messages, (d) an alphanumeric broadcast domain operator name and a specific operator greeting, (e) information concerning changes in broadcast messages, and (f) information concerning correct subchannels. By receiving the index message, a user of the mobile station can gain access to selected ones of the cell broadcast messages.